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Tissues Part 2 - Epithelial Tissue (your body needs order to function…
Tissues Part 2 - Epithelial Tissue
your body needs order to
function
Proper Epithelium: covers and lines your outer and inner body
protects your whole body inside and out
Glandular Epithelium: forms your glands and secretes hormones and other substances
all epithelial tissues are
avascular
this means they are not associated with or supplied by blood vessles
instead they rely on blood supply from surrounding connective tissues
Shape and Layering:
shape of individual cells and the number of layers that they form in.
3 basic shapes:
Squamous - flat (squished like fish sclaes)
fast absorption and disffusion, making thin membranes
Cuboidal - about as tall as they are wide
absorb nutrients, produce secretions (Sweat)
circular nucleus
Columnar cells - tall and thick
cushion underlying tissues
nuclei are stretched
they also absorb nutrients and produce secretions
squamous cells are flat so oxygen can move across them easier - see them in areas where transportation is important (ex. air sacs in your lungs)
if they need to make mucus or hormones - need to be cubular or columnal - stomach lining is made of these
in places where you loose a lot of cells (like your mouth) you have squamous cells because they are
cheaper
to make (don't take as much time, energy and raw material as the others do)
Shape is very important in function
Layering: Simple epithelium, stratified, pseudostratified
Simple Epithelium
one layer of cells
Stratified
multiple layers set on top of each other, like bricks
Pseudostratified
mostly just one layer combined of cells with different shapes and sizes
When classifying cells in a lab you talk both about it's shape and layering: ex. Simple Squamous epithelium
single layer of cells that are flat, scale-like
Stratified Cuboidal tissue
layers of cube shaped cells
Creates order among your organs:
These cells are polar:
Apical (upper) - exposed to the outside of your body or whatever internal cavity it is lining
Basal side - tightly attached to basement membrane
mostly collagen fibers that anchor it to the connective tissue
Semi-permeable
allowing some levels of absorption, filtration, and excretion of substances
Glands
two different types of glands: endocrine and exocrine
Endocrine: secrete hormones right into your bloodstream or to nearby cells
Exocrine: secrete their juices into tubes or ducts that lead to the outside of the body
ex. sweat, saliva, mucus, milk - fill into ducts where they will be secreted to the outside